Cryptamphorella crassilabrosa Dumitrică, 2022

Dumitrica, Paulian, Dieni, Iginio & Massari, Francesco, 2022, Valanginian Radiolarians Of Ne Sardinia (Italy) In The Frame Of The Weissert Event, Acta Palaeontologica Romaniae 18 (2), pp. 97-159 : 124

Cryptamphorella crassilabrosa Dumitrică n. sp.

Fig. 10 t-t2

1997 Zhamoidellum parva (Tan Sin Hok) – Meyerhoff Hull, p. 47, pl. 37, figs. 1, 2.

Description. Shell small, ovoid. Cephalis small, rounded conical externally, its distal half included in the thoracic wall and cavity. Thorax much larger than cephalis, truncate conical, with small and irregularly distributed pores, and strongly asymmetrical in dorso-ventral direction. Collar boundary marked by a small constriction resulted from the brusc enlargement of thorax. Sutural pore large and protruding, with relatively thick and rounded border and migrated on the middle part of thorax. Judging from external morphology, it is impossible to see how much of if its distal part is included in the abdominal cavity. Abdomen spherical with slightly polygonally framed circular pores of variable size and irregularly quincuncially arranged. Lumbar boundary well marked externally by a change of outline resulted by the difference between the diameters of thorax and abdomen. Abdomen without distal aperture.

Studied material. A single specimen in the sample OZ837.

Holotype. The illustrated specimen, coll. MGP-PD, stub PD120 -OZ837- R06-13 , 13 a, 13b.

Dimensions. Hight of shell 110 µm, hight of external part of thorax 27 µm, of abdomen 73 µm, diameter of thorax at base 67 µm, diameter of abdomen 93 µm.

Etymology. From the Latin crassus, - a, - um = thick and labrosus, - a, - um = lip-shaped, namely with big lips, due to the well-developed protruding margins of the sutural pore.

Remarks. This species differs from many other congeneric species from the late Valanginian Sardinian radiolarian assemblageby having the thorax rather large by comparison with the abdomen and the sutural pores displaced up to the level of the upper part of the thorax. Morphologically, it resembles very much the species illustrated by Meyerhoff Hull (1997, p. 132, pl. 37, figs. 1, 2) as Zhamoidellum parva (correct parvum) (Tan Sin Hok), generic translation from Tricolocapsa parva Tan Sin Hok, 1927, p. 47 , pl. 9, fig. 55 and erroneous determination. Or, the Sardinian species has in commom with Tan’s species only the larger size of the thorax, but differs from it by the size and disposition of pores (in Tan’s species the pores are rare, smaller, irregularly scattered and the surface is smooth), and the absence of the large sutural pore. It is possible that the upper Valanginian species shows an evolution of the position of this pore because in the upper Tithonian species illustrated by Meyerhoff Hull, it is on the upper part of the abdomen and just a little above the level of the lumbar constriction.

Range and occurrence. Upper Tithonian of western north America to upper Valanginian of Sardinia. Species very rare .

Figures

Fig. 10 a-c1 - Hemicryptocapsa (?) bellireticulum (Wu & Li): a - OZ825, b - OZ836. c - OZ838, c1 - OZ824. d-f, j-j2 - Williriedellum labeosum Dumitrică n. sp.: d, e, j-j2, OZ837, f - OZ834. g, g1 - Cryptamphorella circumthoracica Dumitrică n. sp., OZ838; g1 - view of apical part. h, k-o – Cryptamphorella dumitricai Schaaf: h - detail of sutural pore, k - OZ825, l - OZ 824, m - OZ838, n-o, OZ839. i, i1- Williriedellum gilkei Dumitrică, OZ838. p - Zhamoidellum ovum Dumitrică, OZ839. r - Williriedellum cordiforme Dumitrică n. sp., OZ837. s, s1 - Williriedellum occultithorax Dumitrică n. sp. in lateral and obliquely apical views, OZ826. t-t2 – Cryptamphorella crassilabrosa Dumitrică n. sp., OZ837: t, t1 - holotype in two positions, t2 – sutural pore much magnified showing inside the wall of the hidden thorax. Figs. a-f, i, h, k-o, r x250; g, gi, h, t, t1 x300.